avformat/framehash: add software version to framecrc/md5

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/utils: use a default lock manager that uses a pthread mutex

That makes avformat & avcodec thread safe without the need to explicitly
register a lock manager.

Reviewed-by: wm4 <nfxjfg@googlemail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>